An optical fiber beat frequency sensing system (BFSS) for multiple human physiological parameters monitoring is proposed. To the best of the authors' knowledge, this is the first BFSS ever reported for multiple human physiological parameters monitoring. By utilizing both fiber Bragg grating (FBG) and fiber laser sensor, not only a low frequency vibration detection with the lowest detectable frequency of 0.25 Hz can be achieved for respiration, heartbeat and pulse signals monitoring, but also human body temperature can be monitored at the same time. Two kinds of beat frequency signals (BFS) are generated in the sensing systems including both polarization laser modes' beat frequency (PMBF) signals and longitudinal mode beat frequency (LMBF) signals. The PMBF signal is utilized for respiration, heartbeat and pulse signals monitoring. Variational mode decomposition (VMD) algorithm is utilized to decompose the monitored time-frequency PMBF signals into single-component respiration, heartbeat and pulse signals. The central frequencies of those signals are obtained by fast Fourier transform (FFT). The LMBF signal is utilized for human body temperature sensing. Measurement results demonstrate that the wearable optical fiber beat frequency digital monitoring system has a simple structure, high signal-to-noise ratio (SNR), stability, accuracy and muti-parameters sensing capability including respiration, heartbeat, pulse and human body temperature without mutual interference.

A compact configurable electromagnetic bandgap (CEBG) filter and a low loss low temperature co-fired ceramics (LTCC) based EBG filter have been proposed. To the best of authors’ knowledge, this is the minimum size configurable BPF ever reported using EBG material. The proposed circuits successfully integrate integrated passive device (IPD) technique based high Q capacitors and LTCC based built in capacitors with EBG substrates. The frequencies of the filters can be easily adjusted by controlling the capacitors. For proof-of-concept demonstration purposes, CEBG filters and LTCC based EBG filters were designed and were experimentally validated from C-band to Ku-band. The measurement results demonstrated the filters’ compact size, wide stop band and reduced insertion loss as working frequency increases. Four LTCC EBG filters are implemented and fabricated with highest working frequency of 17 GHz, a minimum insertion loss (IL) of 1.91 dB, and a 3-dB fractional bandwidth (FBW) of 3%. The CEBG filter demonstrated a compact size of 1.6 mm×1.35 mm, a configurable frequency from 6.88 to 13.5 GHz with an almost constant FBW. Insertion losses of the EBG filters reduce as their working frequencies increase which shows an excellent high frequency application capability of the filters.

A multi-longitudinal mode fiber laser sensor (MLMFLS) system with high signal-to-noise ratio (SNR) is proposed. To the best of authors’ knowledge, this is the highest SNR ever reported by MLMFLS system. The laser sensor consists of a narrow-band fiber Bragg grating (FBG), erbium-doped fiber (EDF) and an optical reflector. The FBG controls the number of laser modes which excited by laser sensor. Beat frequency signals (BFS) modulated by applied measurand are generated by those laser modes and their SNR are controlled by the FBG. Measurement results show the BFS have SNR of 65.0 dB, accuracy of ± 2.0 με, and stability of 0.4 kHz, which demonstrate its high SNR, accuracy and stability.